How do manufacturers determine tripod capacity?

[Nigel Smith]

On the weekend I was putting my camera away in the back of the car only to turn around to see my 26kg (57lb) son happily performing a monkey impersonation on my baby Manfrotto (190 with 141RC head). The legs where flexing but she didn't collapse! He was advised against repeating his performance on my Berlebach sitting alongside although by rights and in comparision, that should let him perform a full routine given the Manfrotto was being tested well outside it's design intentions!

[george jiri loun]

Frank, that makes perfect sense - it's much more difficult to sit on a monopod than on a tripod...